Conventionally, a fuel cell system is known which uses a high-temperature operating fuel cell such as a solid oxide fuel cell (SOFC) or a molten carbonate fuel cell (MCFC). A solid oxide fuel cell (SOFC) operates in a high temperature range of about 600° C. to 1000° C. and a molten carbonate fuel cell (MCFC) operates in a high temperature range of about 500° C. to 900° C.
Conventionally, when the supply of fuel gas is stopped due to natural disasters such as an earthquake, a power failure, a lightning strike, or a typhoon, a fuel cell emergently shuts down (for example, see Patent Literature 1).
Conventionally, after the operation of a fuel cell is stopped, maintenance or the like is performed and the operation of the fuel cell is restarted (for example, see Patent Literature 2).